One animal of the North American Desert that avoids the grim surface conditions by living below the desert is the spink, whose body is about 3 inches (7.7 centimeters) long. It has long since given up flying. Instead, its wings have become adapted to digging. One the underside of each wing, the feathers have become horny scales, forming an abrasive surface. The articulation of the spink's forelimbs has also changed radically. Instead of flapping in time as birds normally do, the front limbs move independently, shoveling away at the earth. The spink crawls in much the same way as it digs, levering itself forward with its elbows, its weight supported by horny pads at the joints.The rest of the spink's body is covered in fine black and white feathers, not unlike the downy feathers of baby emperor penguins in the Quaternary. However, with their elongated bodies, spade-like forelimbs and strange, crawling gait, spinks bear little resemblance to other birds. They also dig with their flat beaks in addition to their spade-wings.
Spinks live in large underground colonies, deep below the inhospitable desert surface. Digging such a vast network of tunnels requires a degree of organization, and the spinks work together. They form chain gangs. The birds first loosen the soil behind them with their wings, passing it to one another along the tunnel. In their dark subterranean habitat, spinks do not need to see. Their eyes have been reduced to mere pinpricks, like the eyes of moles. They communicate by sound or touch, twittering and squeaking in the tunnels.Nearly all individuals are biologically juvenile, having never reached the reproductive stage. Only one female member of the colony, a queen, will mate and lay eggs. She is able to deposit hormones within the egg that determine the sex of the baby and whether it will be able to breed or not. All the work of the colony resolves around keeping the queen alive and nurturing the brood.
The spink's diet consists of the same desert turnip favored by the desert rattleback. Spink colonies are established where turnips are most abundant. Due to the limited food supply, the few fertile males and female pair up to establish new colonies, traveling across the desert in search of desert turnip plants. Spinks are in great danger on the desert surface and so they emerge from their tunnels only under the cover of night, they do this to both find new turnip sites and to mate. First the males emerge and start displaying by flapping their spade-wings. The females emerge second, but they do not head for the nearest displaying males, but instead leave their own colonies to find the display grounds of distant unrelated males. During the early mornings and late afternoons, hungry predators are about.
A colony and its tunnels can be beneath a patch of desert turnips since the turnips took root, and eventually the ground will become unstable. Sometimes, desert rattlebacks will find holes with spinks kicking sand out, and the rattlebacks know that wherever there are spinks there are bound to be turnips. Sometimes, though, deathgleaners will circle overhead and wait for the rattlebacks to unwittingly dig up any spinks. When unearthed spinks are in a state of panic, they crawl clumsily across the desert surface looking for shelter, but their efforts are hindered by their virtual blindness, now made worse by the light of the sun. They are then exposed to predators like deathgleaners.